Continuous horizontal casting in a sacrificial web



F. J. RADD Sept. 26, 1967 CONTINUOUS HORIZONTAL CASTING IN A SACRIFICIAL WEB 2 Sheets-Sheet l Filed Feb. 24, 1965 INVENTOR. FREDERICK J. RADD F. J. RADD 3,343,590

CONTINUOUS HORIZONTAL CASTING IN A SACRIFICIAL WEB Sept. 26, 1967 2 Sheets-Sheet 2 Filed Feb. 24, 1965 FIG. 4

INVENTOR.

FREDERICK J. RADD BY w 4 MM).

ATTORNEY United States Patent 3,343,590 CONTE UOUS HORIZONTAL CASTING IN A SACREFICIAL WEB Frederick J. Radd, Ponca City, Okla, assignor to Continental Oil Company, Pouca City, Okla, a corporation of Delaware Filed Feb. 24, 1%5, Ser. No. 434,867 5 Claims. (Cl. 164-37) ABSTRACT OF THE DISCLOSURE Molten materials are continuously cast in a mold comprising a supported sacrificial web, by regulating the web speed to maintain a freezing zone at a constant location.

This invention relates to continuous horizontal casting. In one aspect, the invention relates to method and apparatus adapted to continuously cast a horizontal rod of a high fusing material, such as steel. In another aspect, the invention relates to a method for continuously casting Within a traveling sacrificial web in a substantially horizontal direction. In still another aspect, the invention relates to apparatus adapted to provide a horizontally traveling sacrificial web mold for continuous casting of high melting material.

There has recently been intense activity in the field of continuously casting high melting materials such as steel. It has been the custom in the production of steel plates or strips, to cast the molten metal, as prepared in the open hearth, into ingots; and subsequently reheating the ingots for reducing in a blooming mill and repeated passes through the rolling mill to reduce the bloom to the desired dimensions for further operations. This requires heavy, expensive machinery which occupies considerable space, and consumes much time and labor.

Attempts have been made to obviate these objections by continuously casting directly from the melt to a semifinished form. These attempts have taken the form of casting in a horizontal or in a vertical direction and, more recently, downwardly at an angle. The molds have taken the form of conveyors, primarily, with such variations as oscillating conveyor segments, electromagnetic melt stirring, etc. Because of the varied attacks on the problem, it is difiicult to enumerate the problems with which the various methods have been beset. However,- some of the more obvious include designing a conveyor tight enough to hold the melt and yet flexible enough and with sufficient temperature resistance to be a continuous loop, obtaining a cooling rate short enough to provide economical throughput and yet consistently capable of producing the desired grain structure, and providing a continuous mold capable of varying product dimensions to suit the market.

Accordingly, one object of the pres-nt invention is to provide method and apparatus capable of continuously casting to a uniform product dimension. Another object is to provide method and apparatus for continuous horizontal casting in a liquid-tight and yet flexible mold. Still another object is to provide method and apparatus capable of varying product slab width and thickness during continuous casting without the necessity of major equipment change or process shutdown. Other aspects, objects and the several advantages of this invention will become apparent upon study of this disclosure, the appended claims and the drawing in which:

FIGURE 1 represents a longitudinal vertical section of an apparatus according to my invention, partially in schematic form, and

FIGURES 2-4 represent vertical transverse sections taken on FIGURE 1.

According to the invention, there are provided, broadly, method and apparatus for continuous horizontal casting comprising a flexible sacrificial web and, in cooperation therewith, traveling conveyor means adapted to hold said web in a predetermined desired form.

I have discovered that high melting materials, such as for example steel, can be cast into a sacrificial web, such as a sheet of random weave ceramic fibers, the web being suitably supported during freezing of the high melting material and later being discarded. I have devised method and apparatus adapted to cast into such a traveling web, and one important aspect of my invention resides in method and apparatus which control variables in my horizontal casting. Another important aspect of my invention resides in maintaining a sacrificial web moving in a substantially horizontal direction, the web being suitably exteriorly supported to provide a channel-like molding zone closed at one end, and in regulating the speed of travel of said web so as to allow the molten material in the molding zone to freeze at a substantially constant locus.

The invention will now be illustrated by reference to the drawing. A roll of web material is adapted to unreel and provide a liner 2 for the traveling mold. The mold comprises a continuous loop conveyor 3, and can be a segmented link, a flexible metal band, or the like. The web 2 is flat as it comes 01f roll 1, and is formed into a trough-like liner within conveyor 3, as .shown in FIG: URES 2-4. The source of molten material to be cast is shown here as a bottom-dumping ladle 4, although it is understood that the source can also comprise a holding chamber or the like. The molten material is poured either continuously or intermittently, as desired, into a pool 5 formed by the web 2 along with the conveyor 3. The conveyor speed is adjusted to provide a residence time in pool 5, taking into consideration the input temperature and the freezing temperature of the material being cast, along with its heat loss rate, to effect freezing of the material near the downstream end of the conveyor in a zone indicated on the drawing as 6. The various adjustments to be described later herein are manipulated so as to maintain the zone of freezing transition 6 at a constant location, and the cross-sectional shape of pool 5 is preferably constant upstream of this freezing zone in order to obtain quiescence of the material just prior to its freezing. The speed of conveyor 3 comprises the primary control over the location of the freezing zone, and can be adjusted responsive to a determination of the location, for example optically, visually or magnetically.

-After the material is frozen, as at 7, it is withdrawn and .draw rolls at a fixed speed relationship with conveyor 3, preferably the same rate, and it can be sheared or otherwise cut into the desired billet lengths. At this point, the web 2 has served its function and will in many instances be quite charred; it can be removed from rod 7 by powered wire brushes or in any other manner as desired, and is discarded.

According to one embodiment of my invention, one control of the final billet thickness, as well as a protection of the billet upper surface, is effected by an additional roll 8 which unreels a web 9 of the same or similar material as web 2. Web 9 is initially floated on the surface of the molten pool 5 at a height determined by roller 10. This roller 10 is moved upwardly or downwardly by a power unit 11, such as for example hydraulic cylinders, and it can be seen that the position of roller 10 will affect the final thickness dimension of billet 7. Power unit 11 can in turn be controlled by sensing means 12, which senses height or thickness of the billet in a suitable manner, as by feelers, light reflection, etc. It is understood that use of the assembly of items 8-12 is optional, but its use allows the billet top surface to obtain a more uniform appearance and to be protected from the atmosphere during cooling by web 9, which is removed later in a manner similar to web 2.

The apparatus of the figure exhibits two other types of adjustment by means of conveyor 3, which will now be described. Major adjustments in the volume of pool are useful when molten material source 4 is operated in an intermittent manner, since it will be seen that the final thickness of billet 7 would otherwise be difiicult to maintain at a predetermined constant level. These major adjustments are made by means of power sources 1322,

which can be similar to source 11. Sources 13-22 move the various respective roller sub-assemblies 23-27, which merely comprise structural members on which are mounted conveyor rollers 28. Each of the sub-assemblies, Which can total as many as desired depending on the size of the apparatus, can be tilted around a horizontal axis perpendicular to the plane of FIGURE 1 and can also be raised or lowered; the tilting can be effected by virtue of pivots 29, for example. It can thus be seen that both the general contour shape and the capacity of pool 5 are adjustable by suitable manipulation of power units 13-22. This manipulation can be responsive to a signal from sensing device 12 or a similar sensing device elsewhere on the solidified bar 7 or on the pool 5, for example sensing means 30. Actuation can be directly in a control loop or can alternately be by an operator observing the output signal of a sensing device. In use, the sub-assemblies 2327 are preferably operated so as to maintain a constant liquid level in pool 5 during periods of major change in that pool. For instance, when source 4 is pouring additional molten material into the pool, the subassemblies are lowered to compensate, and conversely, when no material is being added to the pool, the subassemblies aregradually raised at a rate which decreases the pool volume equal to the output rate of material as product 7. As mentioned earlier, the shape of the pool just upstream of the freezing zone 6 is important in that quiescense must be maintained here, and to this end certain of the rollers on downstream sub-assembly 27 are individually adjustable by virtue of power sources 31. These sources 31 allow fine adjustment of the product thickness in conjunction with roller 10, when used, and also allow changing the contour of the pool in the critical zone. Of course, it will be realized that these adjustments can be eliminated if desired, but their presence is desirable in the best functioning of this invention. According to one embodiment of my invention, the molten pool 5 can be partially or completely divided into two pools for a desired interval of time, as during addition of large amounts of charge liquid to the pool. This is effected by elevating one or more of the roller assemblies intermediate the length of the pool such that the bottom of the pool takes on the form of a rounded-off Greek w. The two pools can be completely isolated, so that large addition of material to the upstream pool is totally without effect on the downstream pool adjacent the freezing zone, or the two pools can be connected by a shallow amount of liquid. The upstream pool thus serves as a major supply pool, and the downstream pool as a product size control and quiescent zone. After the charge is added, the pools can again be converted into one pool, as shown in the drawing, by suitable manipulation of the roller assemblies.

One unobvious advantage of the practice of horizontal casting by my invention resides in the fact that impurity inclusions in the product can be substantially decreased by proper adjustment of the quiescent zone slope just upstream of the freezing zone 6. Although I do not wish to be so bound, I theorize that this occurs by rejection of the inclusions from the quiescent zone simply by gravity,

and they accumulate, near the bottom of the pool, where they can be cleaned out either by periodic shutdown of the apparatus and emptying of the pool to produce a tail product with a high inclusions content or by a forcing out of the dirty liquid and then replacing with a fresh,

liquid of lower impurity content, without process interruption because of the two-pool effect as described.

My invention also includes what might be termed a minor adjustment, which can be effected by pivoting all sub-assemblies 23-27 as one assembly 32 around a pivot point axis indicated in the drawing as 33. This point 33 is preferably located in an upstream portion of freezing zone 6, so that manipulation will have the least effect on the quiescent zone. This adjustment can be effected by a power source 34, similar to, e.g., source 11. Operation of source 34 effects a pivoting of the entire upper run of conveyor 3 around point 33, with the net result being a slight tilting upwardly or downwardly of the entire pool 5 around point 33.. This has the effect of changing the head of molten material against the freezing zone, and will produce minor changes in the thickness of the product bar 7 without changing the shape of pool 5. Rotation around point 33 is preferably effected in response to measurement of the thickness of solid bar 7. A final variable in the process is the speed of conveyo 3, which is adjusted so as to maintain the location of freezing zone 6 constant with respect to the apparatus. Draw rolls, not shown, are also preferably operated at the same speed as conveyor 3.

Reference is now made to FIGURES 2-4, which serve the dual function of illustrating the changing cross-sections through the length of pool 5 and also of illustrating various embodiments of conveyor type suitable for practice of my invention. The conveyor 3 illustrated in FIG- URE 2 comprises an endless flexible band, such as of stainless steel, which is maintained in the desired crosssectional shape by rollers 28; these rollers are fixed laterally into the desired configuration at any given location along the length of pool 5, but are adjustable up or down as a unit, as described in conjunction with FIGURE 1. The sacrificial web 2 is thus supported as desired. In FIGURE 3, the conveyor is of the segmented or link type, as known in the art, each segment comprising a bottom plate with side plates hinged thereto. The side plates are held in the desired configuration for a given location along the pool by rollers 28, and the web 3 is thus held in the desired shape. The conveyor in FIGURE 4 is very similar to that of FIGURE 3, except in the present instance the side sections of a given conveyor segment are slideably held into the bottom section by, e.g., dovetail devices indicated schematically as 35. This latter design has the advantage of providing a rectangular crosssection at all times. The side portions of conveyor sections 3 are urged inwardly against the molten liquid'head by fixed rollers 28, and again the web 3 is supported as desired. It is obvious that conveyor 3 can be either heated or cooled, directly or indirectly as desired, as known in the art.

It will also be obvious that the entire device of FIG- URE l, or as much thereof as desired, can be enclosed in a suitable chamber for blanketing with inert gas. It is presently preferred that the inert gas blanket, when desired, includes the elements of FIGURE 1 with the exception of supply rolls 1 and -8, and liquid source 4. Entry points of webs 2 and 9 into the chamber are easily sealed,

and the rolls are readily renewed by splicing when located solidifying slab and into the liquid pool, as previously explained. Also, the present invention produces a freezing zone which traverses the entire length and encompasses the entire width of the product slab without interruption at a uniform rate during production, which provides uniformity in product properties, as opposed to many prior art horizontal casting processes where the casting is only semi-continuous in large open traveling mold segments. The present invention allows ready adjustment of the cross-sectional size of the final product both as to thickness and width and as to length. The outer surfaces of the product can be screened from atmospheric degradation by the web which lines the conveyor mold in conjunction with the covering web if desired.

A wide variety of materials are suitable for the web of my invention, and the choice of material will depend largely on the temperatures to which it is subjected during the process. It is obvious that simple webbing such as a thin kraft paper can be used when casting a relatively low melting material such as wax. On the other hand, casting of, e.g., steel requires a rather more durable web, as, for example, a ceramic fiber mat. An important feature of my invention resides in considering the web to be a sacrificial lining for the mold, with no attempt being made to reclaim it for direct re-use. Suitable web materials for casting steel include various fibrous inorganic cloths, with or without integral wire reinforcing. One example is Carborundum Company L-l44T cloth, which is an aluminum silicate cloth containing stainless steel wire reinforcing and which contains no organic or combustible materials. The cloth is preferably of a random weave, and can be coated with a glass-forming powder composition to assist in making a liquid-tight web. It can comprise a single or multiple layers. In addition to the aluminum silicate, other inorganic fibers include calcium silicate and aluminum oxide. Although the web must maintain some strength at rather high temperatures in casting steel, it is obvious that the web can be of simpler material for casting lower melting products. For example, sulfur, wax or other materials freezing above ambient temperature can be cast in a kraft paper sheet by the method of my invention.

Further understanding of the invention will be gained from consideration of the following specific example.

Example A melt was made up in proportion of about 6 kg. ingot iron, 100 g. standard ferromanganese and 40 g. ferrosilicon. This melt was cast into channel-shaped molds made from Carborundum Company L-144T cloth, suitably supported on the outside to maintain the channel shape. The steel was poured at about 3000 F. The product ingots had the shape of the mold, and were clean and uniform on the bottom and side surfaces where they contacted the cloth Web. Their upper surfaces showed some oxidation, since they were not protected by either a top web or an inert atmosphere. The cloth web held its shape throughout the pour for a sufficient time to allow complete cooling of the ingots.

Having thus described the invention by providing specifie examples thereof, it is to be understood that no undue limitations or restrictions are to be drawn by reason thereof and that many variations and modifications are within the scope of the invention.

I claim:

1. The method of continuously casting a fusible material which comprises:

(a) providing a source of said material in molten form,

(b) continuously passing a sacrificial web of heatresistant material in a substantially horizontal direction, said web being externally supported so as to define a molding zone open at the top and one end thereof,

(c) passing molten material from said source to said molding zone,

(d) regulating the speed of travel of said web so as to maintain at a constant predetermined locus a transition of said molten material from the molten to the solid state, and

(e) subsequently removing a substantial portion of said web from the cast material.

2. The method of continuously casting a fusible material which comprises:

(a) providing a source of said material in molten form,

(b) continuously passing a sacrificial web of heatresistant material comprising a fibrous inorganic sheet in a substantially horizontal direction, said web being externally supported so as to define a molding zone open at the top and one end thereof,

(0) passing molten material from said source to said molding zone, and

(d) regulating the speed of travel of said web so as to maintain at a constant predetermined locus a transition of said molten material from the molten to the solid state.

3. The method of continuously casting steel which comprises:

(a) providing a source of molten steel,

(b) continuously passing a sacrificial web of heatresistant material comprising a fibrous inorganic sheet in a substantially horizontal direction, said web being externally supported so as to define a molding zone open at the top and one end thereof,

(0) passing molten steel from said source to said molding zone, and

(d) regulating the speed of travel of said web so as to maintain at a constant predetermined locus a transition of said molten steel from the molten to the solid state.

4. The method of claim 3 wherein said molding zone is maintained in an inert atmosphere.

5. The method of claim 3 wherein the shape of said web is controlled so as to provide a quiescent zone immediately upstream of said locus.

References Cited UNITED STATES PATENTS 1,956,462 4/ 1934 Knuth. 2,676,3 69 4/ 1954 Stark 225 7.4 2,692,411 10/1954 Brennan l 2258 X 3,023,468 3/1962 Hord et a1 222165 3,110,941 11/1963 Fagg 2257.4

FOREIGN PATENTS 514,956 7/1955 Canada.

J. SPENCER OVERHOLSER, Primary Examiner. R. S. ANNEAR, Assistant Examiner. 

1. THE METHOD OF CONTINUOUSLY CASTING A FUSIBLE MATERIAL WHICH COMPRISES: (A) PROVIDING A SOURCE OF SAID MATERIAL IN MOLTEN FORM, (B) CONTINUOUSLY PASSING A SACRIFICIAL WEB OF HEATRESISTANT MATERIAL IN A SUBSTANTIALLY HORIZONTAL DIRECTION, SAID WEB BEING EXTERNALLY SUPPORTED SO AS TO DEFINE A MOLDING ZONE OPEN AT THE TOP AND ONE END THEREOF, (C) PASSING MOLTEN MATERIAL FROM SAID SOURCE TO SAID MOLDING ZONE, (D) REGULATING THE SPEED OF TRAVEL OF SAID WEB SO AS TO MAINTAIN AT A CONSTANT PREDETERMINED LOCUS A TRANSITION OF SAID MOLTEN MATERIAL FROM THE MOLTEN TO THE SOLID STATE, AND (E) SUBSEQUENTLY REMOVING A SUBSTANTIAL PORTION OF SAID WEB FROM THE CAST MATERIAL. 